A MOLECULAR-DYNAMICS SIMULATION STUDY OF CHLOROFORM

Three different chloroform models have been investigated using molecul ar dynamics computer simulation. The thermodynamic, structural and dyn amic properties of the various models were investigated in detail. In particular, the potential energies, diffusion coefficients and rotatio nal correlation times obtained for each model are compared with experi ment. It is found that the theory of rotational Brownian motion fails in describing the rotational diffusion of chloroform. The force field of Dietz and Heinzinger was found to give good overall agreement with experiment. An extended investigation of this chloroform model has bee n performed. Values are reported for the isothermal compressibility, t he thermal expansion coefficient and the constant volume heat capacity . The values agree well with experiment. The static and frequency depe ndent dielectric permittivity were computed from a 1.2 ns simulation c onducted under reaction field boundary conditions. Considering the fac t that the model is rigid with fixed partial charges, the static diele ctric constant and Debye relaxation time compare well with experiment. From the same simulation the shear viscosity was computed using the o ff-diagonal elements of the pressure tensor, both via an Einstein type relation and via a Green-Kubo equation. The calculated viscosities sh ow good agreement with experimental values. The excess Helmholtz energ y is calculated using the thermodynamic integration technique and simu lations of 50 and 80 ps. The value obtained for the excess Helmholtz e nergy matches the theoretical value within a few per cent.